you an still get Bardhal Instead of lead gold, it contains MMT as an octane booster which also protects valves. I have used this for years before a got some modern stuff, and it works very well as octane booster and as a valve protector.
Rod
It is true that Bardahl contains MMT (methyl cyclopentadienl manganese tricarbonyl); and that it DOES help with protecting the Airhead pre-1981 (or pre-1980) exhaust valves and exhaust valve seats. It is, probably, the closest thing to TEL (tetraethyl lead) for protection. It isn't as good.
It needs reasonable concentration for its effects. BTW....few know this....but it is not only pre-1980 Airheads that need TEL or some at least reasonable additive (if the valve seats are stock); but, the very earliest K bikes had susceptible valve seats too. Luckily, they are water cooled, and vastly less susceptible.
Sooner or later, the early Airheads will need a top end job, at which time the seats really should be upgraded.
Snowbum